This invention relates to the conditioning of optical soliton bit streams, and finds particular, but not necessarily exclusive, application in the conditioning of such bit streams preparatory for data detection at a receiver.
One of the factors complicating the detection of data in a soliton bit stream at a receiver is that, on the one hand the mark/space ratio of soliton bits is relatively small in order to avoid soliton/soliton interactions, while on the other hand the timing of the solitons is liable to become contaminated by jitter in their transmission from transmitter to receiver.
EP 0 555 063A discloses that the jitter can be removed by the use of a modulator to gate the solitons. For this gating operation, a portion of the incoming signal power is tapped off and used for clock extraction, the extracted clock signal being used to drive the modulator. Jitter is removed from the bit stream by making the period over which the modulator is transmissive short compared with the spread in time-of-arrival (jitter) of the solitons, and accordingly the bits transmitted by the modulator have the timing of the extracted clock signal. In the case of removing jitter from a time division multiplexed soliton bit stream, EP 0 555 063A discloses demultiplexing the bit stream, and employing a separate modulator for each of the separated channels.